Process for producing lubricating oil



Feb. 18, 1936. u. B. BRAY PROCESS FOR PRODUCING LUBRICATING OIL OriginalFiled Oct. 6. 1950 INVENTOR //rlc r'g AORNEY.

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lPatented Feb. 18, 1936` Ulric B. Bray, Palos Verdes Estates, Calif.,as-

signor to Union Oil Company of California, Los Angeles, Calif., acorporation of California Original application October 6, 1930, SerialNo. 486,724. Divided and this application October 14, 1933, Serial No.693,644

Claims. (Cl. 196-19) This y invention relates to the production loflubricating oils from crude oils containing asphalt and wax. Theinvention relates particularly to the separation of wax from waxcontaining oils in 5 the presence of a chlorinated hydrocarbon solventsuch as dichlorethylene and trichlorethylene. This case is a `divisionof my co-pending application Ser. No. 486,724, tiled Oct. 6, 1930.

It has been found advisable to cause the separation of asphalt from theoil by means of volatile solvents which are capable of dissolving theoil and any Wax and which do not dissolve the as- 'phalt Such solventsare lightr petroleum fractions, such as casinghead gasoline and naphthaand also petroleum fractions-normally vaporous at ordinary temperaturesand pressures. Other solvents which may be used are alc'ohol, ether,

mixtures of alcohol and ether, acetone, etc. Il

prefer to use as solvent propane or liquid propane and by this I intendto include such hydrocarbons as are normally vaporous at ordinarytemperature and pressure; such hydrocarbons include methane, ethane,propane, butane, isobutane and mixtures thereof. These normally gaseoushydroy carbon solvents maybe obtained by rectication of casingheadgasoline by the so-called stabilizin'g` method now conventional in thenatural gasoline industry. They are liquefied bycom- .pression andcooled in the conventional manner and are drawn oi into pressure chamberwhere they are maintained in a liquid state until used.

A typical analysis of such a' fraction is 6.72%`

in an asphalt substantially free of oil and a solution of oil in theliquid petroleum fraction. This solution contains substantially all thewax present in the crude oil.

` A It has also been found that oil containing asphalt and impurities,such as Wax, may be first freed from the 'asphalt by a primaryextraction with a light solvent, such as the solvent described I above,and that the impurities, such as wax, may

then be removed at a suitable temperature by the aid of a heaviersolvent such as chlorinated light hydrocarbons as dichlorethylene and inparticular, trichlorethylene in Which the wax is substantially insolubleat the low temperature employed.

By heavier solvent, I mean one of higher .bolling point than the lightsolvent previously described. l

Advantage is taken-of the high volatility of the light solvent 'to causea cooling of the oil upon 5 a release of pressure to produce theseparation of the contained wax. A` further advantage in cooling the oilin this manner is to bring the oil to a proper temperature for acidtreatment. By acid treatment I intend to include treatment with 10 acidfollowed by the step of neutralization and/or clay treatment.

` also encountered in chemically treating oils of high viscosity. Myinvention avoids these diniculties by mixing the oil withtrichlorethylene before dewaxing to reduce the viscosity and place theoil in proper condition for dewaxing. The re- 25 duced viscosityiis alsoadvantageous in chemical treatment of the oil. Instead oftrichlorethylene, I may use other solvents or diluents, for instance,

l benzol, alcohols, such as methyl, ethyl, propyl,

butyl alcohol or mixtures of the same, ketones 30 such as acetone ordiethyl ketone, or mixtures of benzol with acetone or other ketones, ormixtures of benzol and butanol or other alcohols.

In addition to the power which trichlorethylene has of reducing'theviscosity of the asphalt-free 35 oil, it also is used as an extractingmedium for Wax or other material whose presence is deleterious in afinished, high grade lubricating oil. The trichlorethylene, if used insuiiicient quantities, acts as a solvent for the oil during the red0movalv of the Wax or other impurities in a marmer similar to the actionof the propane solution during the removal of the asphalt. By regulatingthe quantity, substantially oil-free wax may be precipitated. Incomparing their volatility and at' produce lubricating oil from oilcontaining asphalt and impurities by extracting the lubricating oililrst with a light solvent such as propaney .to precipitate the asphaltand then extracting the oil from the impurities such as wax with aheavier solvent such as trichlorethylene.

It is a'further object to produce lubricating oil from the oil describedabove by maintaining pressure on the oil and light solvent during theextraction of the asphalt and to extract the impurities such as wax fromthe asphalt free oil by means of a heavier solvent under reducedpressure.

It is furthermore an object of my invention to produce lubricating oilfrom oil containing asphalt and wax by mixing this oil with a solvent inwhich the lubricating oil fractions and wax are soluble, but in whichthe asphalt is insoluble, and subsequently separating the wax from thelubricating oil fractions in the presence of trichlorethylene.

It is a further object of this invention to mix the trichlorethylenewith the oil either in the presence of substantially all the propaneused to precipitate the asphalt, or in the presence of only a portion ofsaid propane, or the trichlorethylene may be added after substantiallyall the propane has been separated from the oil and wax.

Another object of this invention is to produce lubricating oil from oilcontaining asphalt and wax by mixing a volatile solvent therewith underpressure to precipitate the asphalt and dissolve the lubricating oilfractions and wax, separate, the precipitated wax under pressure, andtaking advantage of the highly volatile characteristics of the solventby releasing the pressure and a1- lowing the solvent to vaporize andconsequently cool the oil and wax, thereby precipitating thel latter,and to separate the wax from the oil in the presence oftrichlorethylene. It is a particular object of my invention to separatethe precipitated wax from the oil solvent solution by means ofmechanical separating devices, particuf larly by means of a centrifuge.Other objects and advantages of my invention will be apparent from thefollowing description of my invention taken from the drawing which showsa preferred schematic arrangement-of apparatus for carrying out myinvention.

Referring to the drawing, topped residuum obtained by distilling crudeoil at a temperature preferably not over 60G-625 F. to remove allfractions up to and including all or a portion of the light lubricatingoil, is taken from tank I and is passed through line 2 to pump 3 and toT 4 where it meets a propane solution of lubricating oil coming throughline I5. The propane and residuum pass through the turbulence or mixingcoil 5 and then into decanter C. The asphalt in the residuum isprecipitated by the propane and settles to the bottom of decanter 6. Theprecipitated asphalt resembling a slurry may be drawn oil from thebottom of the decanter with sufficient liquid propane to permitpumping.The asphalt propane slurry is passed through pump 'i and line I where itis mixed with propane from storage 8 via pump 9 and line I0. The mixturethen is passed into mixing coil II and into decanter I2. Decanters 6 andI2 and propane storage 3 are maintained at the same pressure by vmeansof equilibrium lines Icontrolled by valves I1'. The pressures in Ii, I2and 3 are sufilcient to maintain the solvent in liquid state at ordinarytemperatures of about 75 F. -For the solvent given above, this pressureis about 125 to 175 lbs. per square inch. If it is desired to produce anlsphalt containing still less oil or wax, the countercurrent washingwith propane may be extended to as many `steps as desired.

The clear overflow from decanter I2, consisting of liquid propane inwhich is dissolved a small amount of lubricating oil, is passed throughlinev I3, pump I4 to line I5 to T 4 where it is mixed with the incomingtopped residuum and passes through turbulence coil 5 into decanter 6',as described above. The asphalt slurry from decanter I2 is drawn offthrough the pressure release valve I3 and flashed through coil I3 infurnace 20.

Suicient heat is supplied in coil I9 to cause vaporization of thepropane and to melt the asphalt. The heatedmixture of asphalt andpropane is now sent into evaporator 2I where superheated steam isintroduced via 22 in order to complete the evaporation of the propaneand to reduce the asphalt to satisfactory ilash and fire specifications.The overhead from evaporator 2i is sent through line 23 to condenser 24which may be a heat exchanger or simple cooler or a combination ofboth.l The products from' condenser 24 consisting of condensed steam andoil together with uncondensed propane are sent to separator 2l. through21 and condensed water through 26. The uncondensed propane from theseparator is sent through line 28 to propane compressor 20. Thecompressed propane is sent through line 3I to line 32 to condenser 33where it is liquefied and passes into propane storage 8. The reducedasphalt is sent to asphalt storage 23. The pressure in 2I is aboutatmospheric, although it may be higher, if desired.

The overflow from decanter 6,' consisting of a more concentratedsolution of lubricating oil and propane is passed through pump 35 andline. 34 through pressure reduction valve 36 where it meetstrichlorethylene from tank 31 passing through pump 38 and valve 39. Inthe operation of cooling chamber 4I, if a very large portion of thepropane is evaporated, the remaining solution would be too viscous andnot of suiiicient difierence in specific gravity between the oil and waxphases to permit satisfactory behavior in the dewaxing operation.Therefore, a suitable quantity of trichlorethylene is added in line 40to the incoming propane solution. The addition of the trichlorethylenealso reduces the loss of propane f in the centrifuging operation if thecentrifuge Is not gas tight in construction.

It is desired to release the pressure upon the propane solution so thatpropane will evaporate from the solution and thereby sufilciently lowerthe temperature of the remaining solution to permit a satisfactorydewaxing operation. The propane solution passing through pressurereduction valve 36 goes through line 40 into cooling chamber 4I which isin eiect a rectifying column held at a predetermined pressurecorresponding to the desired dewaxing temperature. As the propaneevaporatee, the temperature of the remaining solution falls to that inwhich the vapor pressure will correspond to that being maintained in thecooling chamber by propane compressor 43. The propane vapors pass outthrough line 42 to compressor 43. The conditions in rectifying column 4Iare maintained by the proper manipulation of valve 38 by controlling thesuction of compressor 43 so that only the solvent is removed and thelubricating oil and trichlorethylene are retained as bottoms. Byreducing the pressure tov substantially atmospheric, a temperature of.-40" F. can be obtained; Substan-V The condensed light oils are removedtially all the propane may be .removed from the solution in rectifyingcolumn 4| or only the necessary quantity may be allowed to vaporizetherefrom in order to provide for sufficient cooling to 'dewax the oil.The compressed vapors leaving ever, if desired, the mixture may befilter pressed -or cold settled to separate the precipitated wax In theevent from the remaining oil solution. cold settling is employed forremoving the precipitated Waxthe wax will settle upwardly and the 4 Waxfree solution is decanted from the bottom of the settler. The centrifugeis operated by motor t1 Whichis positioned outside a gas tight insulatedchamber t8 which contains centrifuge t6.

l Wax is discharged from the centrifuge through line ill connecting withthe center of the centrifuge on account of the high specific gravity ofthe trichlorethylene solution of oil and the comparatively lowerspecific gravity of the precipitated wax. The discharged wax may beworked up in any' suitable manner for the recovery of propane,trichlorethylene and oil.. The dewaxed oil is discharged through line5l] and is passed into heater 5 l The heater 5l may consist of anyconvenient equipment which will impart heat to the cold oil passingthrough line 5t, such as a heated coil set in a furnace or heatexchanger. As shown, it Ais a steam heated, steam entering at 52 andexiting at 5i; The 'dewaxed oil solution leaving heater 5l may be sentby either of two courses.

If it is desired to acid and alkali treat the devi/aired lubricating oilstock while in trichlorethylene solution, the oil is passed throughvalve 5d to evaporator 55. In evaporator 55 practically all of theremaining propane is removed from the solution, passed` through mistextractor .55', through line 55 to propane compressor 30, where it iscompressed and sent through line 3l and line 32 to condenser 33 where itis liquefied and passed into propane storage t. The column 55 isoperatedto keep the trichlorethylene in the oil by the proper manipulation ofvalve 5t and by controlling the suction of propane compressor 3. This ismerely a simple rectifying step. Rectifying plates may be provided toassist in this operation as will be understood by those skilled in theart. If desired, the dewaxed trichlorethylene solution of oil may bechemically treated in the presence of the liquefied normally gaseoushydrocarbon solvent, i. e. propane, in which case the propane isretained in the trichlorethylene solution during the subsequentchemicall treatment hereinafter described. A temperature of about 40 F.is desirable in the following chemical treat- -ment and may be obtainedby heating the cold temperature in heatacid sludge is withdrawn throughline 68 controlled by valve 59. In agitator 13 it is first treated withwater passing from 18 via pump 19 and line controlled by valve 80'through line 11. The water is withdrawn through 8l controlled by valve82. The oil is then treated with caustic soda passing from 14 via pump15 and line 16 controlled by valve 16 to line 11. The spent caustic iswithdrawn through 8l. The alkali treated oil is then Washed with wateras previously described. The treated trichlorethylene solution iscarried from agitator 13 by line 33. T-he treated trichlorethylenesolution passes through line 83, pump 8i, line 85, valve to heatinterchanger 81.A

If it is not desired to perform the acid and alkali treatment in thelpresence of the trichlorethylene, the Aoil leaving heater 5I is passedthrough valve 54 to heat interchanger 81, valves 54 and 86 being closedand valve 54 open.l Oil leaving 81, where its temperature is raisedsomewhat, is sent through line B8 to coil 89 in furnace 2li where itstemperature is raised still further before being introduced intoevaporator 9| through line 90. Steam isintroducedvia 92 in evaporatorSil to aid in the flashing of the trichlorethylene and residual propaneand to reduce the remaining oil to satisfactory flash and firespecifications. The oil remaining in the bottom of evaporator 9i isdrawn oir through line 93 and sent to dewaxed oil storage 95 via pumpgli.

If the oil has not been chemically treated in trichlorethylene solution,it may now be treated free from trichlorethylene or, if desired, aquantity of liquefied normally gaseousA hydrocarbon solvent, such asliquid propane, may be added to the trichlorethylene free oil and thechemical treatment may be effected in the presence o f this solvent. i

The treated trichlorethylene solution travels from heat interchanger t1in the same path described above in order to be free of trichlorethyleneand residual propane.

The overhead from evaporator 9i is passed through 95 and heatinterchanger B1 into line 91 The trichlorlineill to trichlorethylenestorage 31. Any uncondensed propane in separator 99 passes through lineWil to propane compressor 3. The compressed propane passes through lines3 and 32 to condenser Siti where it lquenes and passes to propanestorage t. The condensed steam is withdrawn through itl.

In the vforegoing description of my invention, I have described achemical treatment of the oil as taking 4place subsequent to the removalof the wax from the oil. be hunted to this exact procedure. Ii' desired,the chemical treatment of 'the oil mayprecede the wax separation stepand may be effected in the presence or substantial absence oftrichlorethylene and/or liquid propane. ethylene and/or liquid propanemay be added to the oil subsequent to the chemical treatment if thelatter has been accomplished in the absence of either or both of thesesolvents.

The following is an example of one mode of carrying out my process forthe production ofA lubricating oil employingl trichlorethylene as asolvent to aid in the separation of the precipitated wax from the oil.vHowever, it is to be-'understood that this example is to be consideredmerely as illustrative and not as limiting m'yinvention:

A topped residuum containing both asphalt and wax -such as Santa FeSprings residuum which has been topped to approximately 400 However, Ido not wish to The trichlor-` seconds Saybolt furol viscosity at 210 I".is comtaining the same which comprises commingling mingled withapproximately 4 volumes of liquid propane at a temperature of about F.and under a pressure of about to 175 lbs. per square inch which issumkcient to maintain the propane in a liquid state at the abovetemperature. The propane dissolves the oil and wax but precipitates theasphalt contained in the oil. After permitting the mixture to settle fora sumcient time, the oil propane solution is decanted away from thesettled precipitated asphalt.

The oil propane solution is then mixed with approximately two volumes oftrichlorethylene based on the one volume of the original toppedresiduum. 'Ihe pressure on the. mixture is gradually released toapproximately atmospheric to permit evaporation of propane which reducesthe temperature of the remaining solution of oil. wax, trichlorethyleneand remaining propane to about -40 F. The reduction in temperaturecauses the wax to precipitate from the mixture. Approximately 2.5 -to 3volumes of liquid propane are evaporated during their refrigeration downto -40 F. leaving from 0.9 to 1.4 volumes of liquid propane associatedwith 2 volumes of trichlorethylene and approximately 0.8 volumes of waxand de-asphaltized viscous oil. This mixture is then centrifuged toseparate the precipitated wax from the oil, propane andtrichlorethylene. Due to the high specific gravity of thetrichlorethylene solution of oil and propane, the wax will appear at thecenter of the centrifuge and the solution of dewaxed oil will appear atthe periphery of the centrifuge bowl. Discharge of wax and the solutionof dewaxed oil as separate phases is accomplished continuously from thecentrifuge. The oil solvent solution is then chemically treated withacid and alkali and/or clay and then the chemically treated solution ofoil is distilled to remove the'liquid propane and trichlorethylene toleave a lubricating oil substantially free from asphalt and wax andhaving a .low Conradson carbon value and low pour point.

It is to be understood that the above description is merely illustrativeof preferred embodiments of my invention of which many variations may bemade by those skilled in the art within the scope of the followingclaims without departing from the spirit thereof.

I claim:

1. A process for separating wax from oil conthe precipitated wax fromthe oil and subsequently separating the liquefied normally gaseoushydrocarbon and chlorinated ethylene from the oil.

2. A process for separating wax from oil containing ythe same whichcomprises commingling said oil with a liquefied normally gaseoushydrocarbon and dichlorethylene, chilling the mixture to precipitate thewax, separating the precipitated wax from the oil in the presence ofsubstantial quantities of liquefied normally gaseous hydrocarbon anddichlorethylene to aid in the separation of the precipitated wax fromthe oil and subsequently separating the liquefied normally gaseoushydrocarbon and dichlorethylene from the oil.

3. A process for separating wax from oil containing the same'whichcomprises commingling said oil with a liquefied normally gaseoushydrocarbon and trichlorethylene, chilling the mixture to precipitatethe wax, separating the precipitated wax from the oil in the presence ofsubstantial quantities of liquefied normally gaseous hydrocarbon andtrichlorethylene to aid in the separation of the precipitated wax fromthe oil and subsequently separating the liquefied normally gaseoushydrocarbon and trichlorethylene from the oil.

4. A process for separating wax from oil containing the same whichcomprises commingling said oil with liquid propane and trichlorethylene,vaporizing a portion of the propane to chill the oil and precipitate thewax, separating the precipitate wax from the oil in the presence ofsubstantial quantities of liquid propane andrtrichlorethylene to aid inthe separation of the precipitated wax from the oil and subsequentlyseparating the liquid propane and chlorinated ethylene from the oil.

5. A process as in claim 4 in which the separation of the precipitatedwax is accomplished 50 by means of a centrifuge.

ULRIC B. BRAY.

